This is an application for a K08 award for Dr. Katherine Bianco, an Assistant Professor of Obstetrics, Gynecology, and Reproductive Sciences at the University of California, San Francisco (UCSF). Dr. Bianco is fully trained in Maternal-Fetal Medicine and Human Genetics. Her primary mentor is Dr. Susan Fisher, a Professor in the same department who has had a great deal of experience training student at all levels and clinician-scientists, in particular. Dr. Fisher's group studies human placentation and stem cell biology. In her proposed mentor's lab, Dr. Bianco has been studying the impact of trisomy 18 and 21 (T18 and T21) on gene expression patterns at the maternal-fetal interface. Global profiling revealed interesting sets of differentially expressed (DE) transcripts that were unique to each condition. In T18, a large percentage of the DE genes were on the affected chromosome, which was not the case for T21. In both instances, the DE molecules included interesting cell cycle and developmental regulators that could play important roles in the phenotypic alterations that are the hallmark of these aneusomies. Thus, the results of these experiments showed the utility of using a global gene expression profiling approach to gain insights into the placental manifestations of T18 and T21. In this context, the candidate hypothesizes that T18 and T21 negatively regulate trophoblast (TB) self-renewal and/or differentiation. Three specific aims are proposed to test this theory. The first uses methods that were recently developed by the Fisher group to derive human trophoblast stem cells (hTSCs) from the chorionic portions of T18 and T21 placentas. The second employs a microarray approach to identify genes that are DE in the aneuploid lines as compared to control (euploid) hTSCs. The third uses a lentiviral approach to assess the functions of molecules that have expression patterns, which are consistent with important functional roles. Thus, the proposed experiments are designed to yield a great deal of new information about the functional deficits that underlie placental defects in trisomy 18 and 21. This information will also enlighten the biology of these syndromes in terms of the molecules that lies downstream of these chromosomal aberrations. Finally, the deficits uncovered will offer new insights into the molecular cascades and pathways that govern TB function in normal pregnancy. In carrying out the planned experiments, the candidate will gain expertise in the experimental approaches that are used to study human placentation with an emphasis on stem cell biology. In the process, she will receive the additional training that she needs to become an independent scientist. The plan includes a first rate mentoring team, an outstanding institutional environment, as well as the full and enthusiastic support of her Department Chair, Division Chief, and primary mentor.